1. Field
The embodiments described below relate generally to delivery of radiotherapy treatment. More specifically, some embodiments are directed to radiotherapy treatment of moving patient areas and systems for delivering such treatments.
2. Description
Radiotherapy or radiation therapy is used to treat cancer and other diseases with ionizing radiation. Conventional radiotherapy systems generate and direct a beam of radiation to a targeted treatment area within a patient volume. The radiation beam is intended to injure or destroy cells within the targeted area by causing ionizations within the cells or other radiation-induced cell damage.
Radiotherapy treatment plans are intended to maximize radiation delivered to a targeted area while minimizing radiation delivered to healthy tissue. In this regard, the treatment of a moving target area poses a challenge to radiotherapy. In some embodiments and contexts of radiotherapy, moving targets intended for treatment by radiation are commonly encountered. For example, stereotactic body radiation therapy (SBRT), which is becoming increasingly popular in the treatment of lung cancer, routinely encounters moving tumors due the motion induced by respiratory breathing.
Effective treatment of moving targets includes detecting and monitoring the motion of the target area, and delivering radiotherapy beams to the moving target. A number of conventional technologies may be used to detect and monitor target motion. Some techniques include providing a device to monitor the rise and fall of an external surface of the patient caused by breathing, while other techniques include providing implantable beacon devices in a patient to directly monitor tumor motion without a surrogate. Some other technologies include using X-Ray imaging. However, each of these technologies for monitoring target motion is separate and distinct from the radiotherapy treatment system and requires devices and/or systems internal or external to the patient.
One conventional method for addressing the delivery of radiation treatment to moving targets includes using an increased margin of delivery around a target that is large enough to account for target excursions from a nominal position. While the increased margin may result in the target receiving a desired radiation dose, surrounding healthy tissue or organs are at an increased risk of also receiving radiation. Gated treatment techniques to address moving targets involve determining a gating window during which the target movement is minimized to deliver the radiation treatment. For example, radiation may be delivered to the target only when the patient is within 80% exhalation of the breathing cycle, a period when motion of the targeted treatment area may be relatively motionless. However, acquisition of planning images (e.g., 4D CT computed tomography) and a breathing monitoring device to provide an indication of the phases of the patient's breathing cycle are needed for this technique. One proposed technique for delivering radiation to a moving target involves using an auxiliary device to determine the location and the shape of the target at any point in time and reshaping the MLC (multileaf collimator) leaves of the radiotherapy system to follow (i.e., track) the target shape at any point in time. However, this technique also requires an auxiliary device in addition to the radiotherapy system.
The present inventors have realized that conventional moving target monitoring and treatment delivery as described above is inefficient and insufficient for radiotherapy treatment of moving targets. In particular, since conventional techniques require additional, auxiliary, external, and/or internal devices and processes to detect, monitor and deliver radiation to a moving target, other systems to provide treatment of moving target areas are desired.